Tìm giới hạn B= lim(x_>2) (x^4-5x^2+4)/(x^3-8)

* Hướng dẫn giải

Chọn D

$\begin{array}{l}B=\underset{x\to 2}{\lim }\frac{x^4-5x^2+4}{x^3-8}\\ =\underset{x\to 2}{\lim }\frac{(x^2-1)(x^2-4)}{x^3-2^3}\end{array}$

$=\underset{x\to 2}{\lim }\frac{(x^2-1)(x-2)(x+2)}{(x-2)(x^2+2x+4)}$

$\begin{array}{l}=\underset{x\to 2}{\lim }\frac{(x^2-1)(x+2)}{x^2+2x+4}\\ =\frac{(2^2-1).(2+\text{}2)}{2^2+2.2+\text{}4}=1\end{array}$